A Techno-Economic Analysis of Solar-Driven Atmospheric Water Harvesting

Water may be produced from atmospheric humidity anywhere on Earth; however, current approaches are energy intensive and costly, thus limiting the deployment of atmospheric water harvesting (AWH) technologies. A system level thermodynamic model of several AWH pathways is presented to elucidate the important energy flows in these processes as a means to reducing the energy required to produce a unit of water. Model results show that fresh water may be produced from humid air via processes driven solely with solar electricity in an arid climate with an energy input between 116 kWhe/m3 and 1021 kWhe/m3, depending on atmospheric conditions and processing configuration. We describe a novel, desiccant-based AWH approach in which the latent heat of vaporization is internally recovered resulting in a significant reduction in energy requirements relative to the state of the art. Finally, a parametric model of a desiccant-based AWH system is used to estimate the minimum levelized cost of water (LCOW) via solar-driven AWH at 6.5 $/m3 when both latent and sensible energy are recovered internally.

A Techno-Economic Analysis of Solar-Driven Atmospheric Water Harvesting

Water may be produced from atmospheric humidity anywhere on Earth; however, current approaches are energy intensive and costly, thus limiting the deployment of atmospheric water harvesting (AWH) technologies. A system level thermodynamic model of several AWH pathways is presented to elucidate the important energy flows in these processes as a means to reducing the energy required to produce a unit of water. Model results show that fresh water may be produced from humid air via processes driven solely with solar electricity in an arid climate with an energy input between 158 kWhe/m3 and 1021 kWhe/m3, depending on atmospheric conditions and processing configuration. We describe a novel, desiccant-based AWH approach in which the latent heat of vaporization is internally recovered resulting in a significant reduction in energy requirements relative to the state of the art. Finally, a parametric model of a desiccant-based AWH system is used to estimate the minimum levelized cost of water (LCOW) via solar-driven AWH at 6.5 $/m3 when both latent and sensible energy are recovered internally.

Simulation of condensation unit in ASPEN PLUS

The article discusses the scheme of deep utilization of the heat of flue gases. It has been established that in boiler units operating on natural gas, the only way to significantly improve the use of fuel is to deeply cool the combustion products to a temperature at which it is possible to condense the maximum possible portion of the fumes contained in the gases. To analyze the main energy indicators of the condensing unit and optimize its operating modes, a priority scheme was simulated in Aspen Plus. In this scheme, there are tees, heat exchangers and a reactor (boiler furnace). The configuration of tees (mixers) is carried out by setting the costs or fractions of two flows entering or leaving the element. The boiler furnace is modeled as a Gibbs reactor, which calculates the chemical and thermodynamic equilibrium by minimizing the difference in the Gibbs energy of the products and the starting materials. Using the Aspen Plus computer program, the condensation unit circuit was simulated at the PTVM-100 boiler unit with the specification of the optimal operating parameters of material flows and heat exchange equipment. The calculations show that when using a condensing boiler, a triple energy effect is achieved: the physical heat of the flue gases is used; the latent heat of vaporization released during condensation is used; the condensate released from the flue gases is used.

Experimental investigation of higher carbon alcohols with low latent heat of vaporization as self rewetting fluids in closed loop pulsating heat pipes

Heat recovery plays an important role in all energy systems. The dissipation of heat is drastically increasing due to the advancement of electronic components. To cool the electronic components many heat recovery devices are introduced and out of which heat pipes play an important role. Pulsating Heat Pipe (PHP) is a new type of heat transfer device which was introduced by Akachi in mid-1990. It is used mainly in the cooling of electronic components because of its potential for removing high heat flux. An experimental study was made to investigate the heat transfer performance of PHP using self-rewetting fluids of high carbon alcohols. The latent heat of vaporization plays an important role in the heat transfer performance of PHP. It was observed that the high carbon alcohols showed a decrease in the latent heat of vaporization. The high carbon alcohols such as 1-Butanol, 1-Pentanol, 1-Hexanol, 1-Heptanol, and 1-Octanol were mixed with the deionized water to form a self-rewetting fluid. These self-rewetting fluids showed a unique behavior due to the inverse Marangoni effect. It was observed that the lower thermal resistance and higher heat transfer coefficient was obtained, especially in the dilute aqueous solution of 1- Octanol.

Thermodynamic properties of water desorption in Buchenavia capitata (Vahl) Eichler

ABSTRACT Thermodynamic properties provide information on energy demand and kinetic parameters in water sorption processes in agricultural products. Such information is essential to analyze and scale drying and storage equipment. The objective of this study was to determine the thermodynamic properties involved in the water desorption process in Buchenavia capitata (Vahl) Eichler seeds with moisture contents ranging from 13.31 to 7.21% dry basis (d.b.), obtained by the indirect static method, at temperatures of 10, 20, 30 and 40 °C. The latent heat of vaporization, differential entropy and Gibbs free energy increase with the reduction of the moisture content of the seeds. The enthalpy-entropy compensation theory is valid for the desorption process, which is controlled by the enthalpy. The desorption of water in the seeds is not a spontaneous process.

Thermodynamic properties of Anacardium humile St. Hil. (cajuzinho-do-cerrado) achenes

The cajuzinho-do-cerrado is a native species of the cerrado of great potential of use and is threatened of extinction. The aim of this study was to determine and evaluate the thermodynamic properties of Anacardium humile St. Hil. achenes from the different hygroscopic equilibrium points according to the moisture content. To obtain the isotherms, the indirect static method was used at temperatures of 10, 20, 30 and 40 °C and for moisture contents of 13.4, 11.1, 8.7 and 5.3% dry basis (db). The Copace model was used to describe the hygroscopic equilibrium of the achenes. The thermodynamic properties are influenced by the moisture content because the latent heat of vaporization of the water of the achenes increases with the decrease in the equilibrium moisture content, varying between 3,035.63 and 2,510.80 kJ kg-1 for moisture contents of 4.51 to 13.4% db, respectively. The differential enthalpy and entropy are closely related to the moisture content of the achenes. The isokinetic temperature of 304.67 K denotes the linear chemical compensation between the differential enthalpy and entropy of the Anacardium humile St. Hil. achenes, and the desorption process is controlled by enthalpy.

Technical note: rectifying systematic underestimation of the specific energy required to evaporate water into the atmosphere

Not all of the specific energy consumed when evaporating water into the atmosphere (λ) is due to the latent heat of vaporization (L). What L represents is the specific energy necessary to overcome affinities among liquid water molecules, neglecting the specific work done against atmospheric pressure (p) when water expands in volume (V) from liquid to gas (pV work). Here, in the one-dimensional context typifying micrometeorology, the pV work done in such an expansion is derived based on the Stefan flow velocity at the surface boundary, yielding a simple function of the virtual temperature; additionally, an empirical formula is provided that approximates λ quite accurately over a useful range of environmental conditions. Neglect of this pV work term has caused a systematic 3–4 % underestimation of λ, and to some extent inhibited closure of the surface energy balance.

Pilot Experimental Study of New Urea Hydrolysis for DeNOx in Coal Plant

Based on the domestically developed urea hydrolysis reactor and urea hydrolysis ammonia process, a pilot test of urea hydrolysis was established with 10kg/h ammonia production for the flue gas denitration reductant, to reduce pollution of NOx emission from coal plant and avoid the environmental risk of liquid ammonia.The results show that urea hydrolysis reaction rate was controlled by the temperature monotonically. Steam consumption increases with the increase of pressure, especially when pressure is greater than 0.6 MPa and bring about lower economy. The higher feed concentration, the lower energy loss for the water latent heat of vaporization, and the lower operation cost of device. The maximum ammonia production is 16 kg/h, the hydrolysis conversion is greater than 98%, and the ammonia mass fraction of product gas is 22.6–34% (volume fraction of 28.5–48.0%) during the tests, at the feed concentration of 40–60%, the operating pressure and temperature of 0.6MPa and 160°C.